This application is related to an application filed concurrently herewith entitled IMPACTOR FOR USE WITH CERVICAL PLATE, by Jeffrey J. Thramann, M.D.
The present invention relates to apparatuses and methods for treating and correcting spinal abnormalities and, more particularly, to cervical plates useful in procedures relating to the insertion of bone grafts in the spine and fusing vertebrae.
The vertebrae of the human spine are arranged in a column with one vertebra on top of the next. Between each vertebra exists an intervertebral disc that transmits force between adjacent vertebrae and provides a cushion between the adjacent vertebrae.
Sometimes, back pain is caused by degeneration or other deformity of the intervertebral disc (xe2x80x9cdiseased discxe2x80x9d). When a diseased disc impinges upon neurological structures or is determined to be a pain generator, surgeons treat the diseased disc by surgically removing the diseased disc and inserting a bone graft in the space vacated by the diseased disc. The adjacent vertebrae are then immobilized relative to one another with a cervical plate and screws. Eventually, the vertebrae grow into one solid piece of bone.
Currently, it can be difficult to insert the bone graft into the vacated space and fuse the adjacent vertebrae. The current process of inserting a bone graft and fusing the adjacent vertebrae will be explained referring to FIGS. 1 and 2. FIG. 1 shows two adjacent vertebrae 102 and 104. Located between vertebrae 102 and 104 is an intervertebral space 106 partially filled by a bone graft 108. When the bone graft 108 is first inserted into the intervertebral space 106, the adjacent vertebrae 102 and 104 are manually kept apart by the surgeon using, for example, a retracting device (not shown). As shown in FIG. 2, once the bone graft 108 is placed, the surgeon releases the adjacent vertebrae 102 and 104 allowing them to squeeze the bone graft 108 and hold the bone graft 108 in place.
To immobilize the vertebrae 102 and 104 with the bone graft 108 in place, the surgeon next applies a cervical plate 202 over the adjacent vertebrae 102 and 104. Cervical plate 202 may have a central viewing window 204 and one or more screw holes 206, in this example four screw holes 206a-206d are shown. Four bone screws, which are identified by reference numerals 208a-208d, and shown in screw holes 206a-206d respectively, would be screwed into the vertebrae using the screw holes 206 to anchor the cervical plate to the vertebrae and immobilize the vertebrae with respect to one another.
As can be appreciated, attaching the cervical plate 202 using the bone screws 208 can be a difficult endeavor. Generally, a temporary screw (also not shown) is placed in one of the screw holes, for example 206a. Bone screw 208c would then be partially screwed into the bone at screw hole 206c. The temporary screw in hole 206a would be replaced by bone screw 208a, which would be tightened. Then the other bone screws 208 would be screwed into the bone in a cross point manner. The ability of the cervical plate to move freely in relation to the vertebrae 102 and 104 and the bone graft 108 until the bone screws anchor the plate causes difficulty in attaching the cervical plate. This is made more difficult because, generally, only a portion of the cervical plate is visible to the surgeon at any given moment (due to space constraints and surgical tools).
While the above example relates to replacement of one intervertebral disc between two adjacent vertebrae, sometimes it is necessary to replace two or more discs spanning three or more vertebrae. The problems associated with replacing one disc become more exacerbated the more discs and vertebrae that are involved.
Due to the small margins for error in placing the bone screws into the vertebrae, it would be desirous to develop a cervical plate that was not as free to move prior to attachment with the bone screws, and one that automatically aligned the screw holes over the adjacent vertebral bodies.
The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings. Further, the advantages and purpose of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To attain the advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, apparatuses to facilitate the insertion of a bone graft into an intervertebral space and positioning of a cervical plate are provided. In particular, a cervical plate having an attachment mechanism that allows a surgeon to attach the bone graft to the cervical plate is provided. The bone graft, when inserted into the intervertebral space, holds the cervical plate in position to facilitate the anchoring of the cervical plate to vertebrae, and by taking advantage of the fixed association of the junction of the graft and the vertebral endplate with the cervical plate, ensures the screw holes of the cervical plate are optimally placed over the adjacent vertebral bodies to further facilitate screw placement for anchoring of the cervical plate to vertebrae.
The present invention further provides an impactor. The impactor is releasably coupled to the cervical plate and has a handle and prongs. The prongs assist in separating the vertebrae to facilitate the insertion of the bone graft, which is attached to the cervical plate via an attachment mechanism, into the intervertebral space.
The present invention still further provides methods for correcting abnormalities of the spine by inserting bone grafts.